1. Field of the Invention
The present invention relates to an electrostatic ink jet recording apparatus, in particular, to an electrostatic ink jet recording apparatus with an ink of which toner particles dispersed in a carrier solution and sprayed by electrostatic electricity so as to record data.
2. Description of the Related Art
A variety of ink jet recording systems have been proposed because of their advantages such as direct recording on plain paper and low noise. As one of such systems, an ink recording head has been disclosed as Japanese Patent Laid-Open Publication No. 56-167473. With reference to FIG. 5, the structure of the related art reference will be described.
In an ink jet recorder, a large number of electrodes 42 are placed at an inner side of an ink jet port 41 of a recording head. An ink in the ink jet port 41 is selectively jetted through the selective by selectively applying a high voltage pulse between the electrodes 42 and a grounded conductor 49 at the side of record paper 50 corresponding to a picture signal. In the ink jet recorder, the ink jet port 41 is divided into an upper part 41a and a lower part 41b with a partition 45 in the slit-form jet port 41, which is formed with an upper plate 46 and a lower plate 47. A large number of electrodes 42 are disposed at the inside of divided jet ports 41a and 41b (upper plate and lower plate surfaces and/or the surfaces of the divided plates). By applying a high voltage to some electrodes and a low voltage to an electrode positioned on the right or left of the electrode, jetted ink dot moves to the high voltage side.
An ink placed in an ink chamber 44 reaches an ink ejection port 41. The ink at the ink jet port 41 forms a linear meniscus. When a high voltage of around 2 kV is applied from a terminal 48 to a selected electrode 42, the ink is jetted from the position of the electrode at which such a high voltage is applied. The ink is accelerated by an electric field with a conductive roller 49 and then adhered to record paper 50. Thus, by selecting a plurality of electrodes and applying a high voltage thereto at the same time, a pattern of one line can be recorded. With the record paper 50 moved, characters, figures, and so forth can be recorded as dots of the ink.
Another related art reference that has been disclosed as PCT Laid-Open Publication NO. WO 93/11866 is an electrostatic ink jet recording apparatus. The apparatus comprises an electrostatic ink jet recording head and a counter electrode. The counter electrode causes an electric field to be formed with a counter electrode against the ink jet recording head disposed on the rear surface of the record paper. The ink jet recording head has an ink chamber and an ejection electrode. The ink chamber temporarily stores an ink solution supplied from an ink tank or the like. The ejection electrode is disposed at an edge portion of the ink chamber. The ink jet recording head is disposed opposite to the counter electrode. The ink solution in the ink chamber is supplied to the edge of the ejection electrode due to the surface tension. Thus, an ink meniscus is formed at the edge of the ejection electrode. The ink solution used for the ink jet recording head contains a coloring charge particles. The charge particles are positively charged with a zeta voltage. When a positive voltage is applied to the discharge electrode, the voltage of the positive electrode of the ink solution increases. When Coulomb force that works between the charge particles at the edge of the ejection electrode and the counter electrode largely exceeds the surface tension of the ink solution, agglomeration of the charge particles with a small amount of ink solution is jetted from the edge position of the ejection electrode to the counter electrode. The charge particles adhere to the front surface of the record medium. In such a manner, with the voltage to the ejection electrode, agglomeration of the charge particles is successively jetted from the edge of the election electrode to the front surface of the record medium and thereby data is recorded.
The diameter of the toner particles is on the order of several microns. Thus, jetted toner particles stably adhere in fibers of plain paper that is normally used as a record medium. Consequently, a heat fixing process for heating and pressuring toner particles on the record medium is not required unlike with a fixing means used in a dry electrophotographic apparatus. In the related art reference, the toner can be fixed with only hot air. This is one advantage over the conventional electrophotographic apparatus with a dry toner.
In the conventional electrostatic ink jet recording apparatus, when the front surface of a record medium is smooth as with coated paper or when the front surface of the record medium is very smooth and the toner particles do not adhere in fibers of the record medium as with an OHP film, the toner particles that adhere on the record medium are easily removed and thereby a fixing failure takes place.
As a means for solving such a problem, a heat fixing unit may be used as with the conventional electrophotographic apparatus with a dry toner.
However, as was described above, with the electrostatic ink jet recording apparatus, the toner can be easily fixed by blowing a small amount of hot air. In addition, the power consumption of the electrostatic ink jet recording apparatus is much smaller than that of the conventional electrophotographic apparatus. Thus, as with the electrophotographic apparatus with a dry toner, the method using the heat fixing unit that requires hot air deteriorates the advantage of the electrostatic ink jet recording apparatus front a view point of the power consumption.